1. Field of the Invention
The present invention relates generally to systems for repairing, lining or expanding conduit, such as expanding a liner conduit within a host conduit and, in particular, to a system and arrangement with accompanying hardware for repairing a conduit, for example expanding a liner conduit within a host conduit.
2. Description of Related Art
Conduit systems are used extensively throughout the world in order to transfer or convey material, such as water and other fluids, from location to location for distribution throughout the system. For example, extensive conduit systems are used to distribute water to both residences and businesses for use and further processes. Typically, such conduit or piping systems are located underground, as aboveground piping would be both unsightly and intrusive.
Typical water conduit systems transport material through pipe, e.g., cast iron, ductile iron, reinforced concrete, asbestos-cement, etc., buried underground with the branches extending in various directions in order to reach the end user. Normally, after many years of use, or for some other reason, the present piping fails and begins to leak, thereby reducing line pressure and unnecessarily allowing water to leak into the area surrounding the piping. Such leaks not only affect the system, but increase the processing costs of the supplier, which, in turn, increases the end user costs. Therefore, these leaks must be quickly repaired and preventative measures taken to ensure that further leakage is prevented.
Due to the underground positioning of the conduit system, repairing a leaking pipe is particularly labor intensive and time consuming. Trenches must be dug along the pipeline to locate the leak and effectively repair it prior to putting the pipe back in service. Various lining systems have been developed according to the prior art in an attempt to seal a leaking pipe or a pipe that has fallen into disrepair, whether to repair a present crack or to preventatively ensure against future cracks or breaks. In addition, the use of a much smaller diameter pipe within the larger diameter cracked or broken pipe has been used. However, this merely replaces the problem of a cracked outer pipe with a cracked or otherwise leaking inner pipe. Still further, using such a pipe-in-pipe system drastically reduces the flow through the conduit system and evidences unwanted and varying pressure parameters.
To that end, a pipe liner and method of installation have been developed, as disclosed in U.S. Pat. No. 5,794,662 to St. Onge et al., specifically directed to pressurized pipeline applications. The St. Onge patent is directed to a method of relining sewer lines, water lines or gas lines, and uses a segmented liner of reduced size relative to the pipe being relined. However, as opposed to merely leaving the small diameter liner conduit within the large diameter outer conduit, the method of the St. Onge patent uses heat and/or pressure to mold the reduced size pipe to the shape of the pipe being relined. In particular, the inner or liner conduit is a thermoplastic pipe, typically a polyvinyl chloride (PVC) pipe that, when exposed to heat or pressure, expands and molds against the inside of an existing conduit to effect the relining of it. This process allows for both the lining of the entire length of pipe or only a portion of it that is damaged, which is typically referred to as “spot repair.”
According to the St. Onge patent, once the length of the liner conduit is inserted into the existing or host conduit, the liner conduit is plugged at either end and exposed to steam under pressure to heat the liner conduit along its length and apply pressure, which urges it to expand and contact the interior walls of the surrounding host conduit. Once the liner conduit has fully expanded to conform to the interior surface of the existing conduit, it is cooled and the plugs are removed. The resulting expanded liner conduit conforms to the walls of the host conduit, thereby preventing any further leakage. Also, the method of the St. Onge patent requires only access pits to be dug at either end of the section to be repaired.
While the St. Onge patent represents an advance in the art of relining or repairing underground conduit systems, there is room in the art for additional improvements and advancements. Merely plugging either end of the liner conduit and injecting steam to pressurize the liner conduit and force it to expand to the walls of the host conduit presents certain problems. Such a method and system give rise to both physical and structural weaknesses at either end of the expanded liner conduit.
Various arrangements and systems have been developed for assisting in the injection of gas and/or liquid into a liner or within a lining process, as is known in the art. For example, hardware and equipment have been developed for use in connection with a bladder expansion or thermoplastic impregnated liner system. See U.S. Pat. No. 6,299,803 to Ledoux; U.S. Pat. No. 5,601,763 to Hunter et al.; U.S. Pat. No. 5,462,706 to McMillan et al.; U.S. Pat. No. 5,503,190 to Kamiyama et al.; U.S. Pat. No. 5,490,964 to Kamiyama et al.; U.S. Pat. No. 5,225,121 to Yokoshima; U.S. Pat. No. 6,050,300 to Schwert et al.; U.S. Pat. No. 4,728,223 to Rice; U.S. Pat. No. 4,671,840 to Renaud; U.S. Pat. No. 4,361,451 to Renaud; U.S. Pat. No. 6,539,979 to Driver; U.S. Pat. No. 5,368,809 to Steketee, Jr.; and U.S. Pat. No. 5,399,301 to Menendez et al. However, such equipment and systems have several drawbacks. Without controlled restriction of the liner conduit within the host conduit, undesirable longitudinal or lateral expansion may occur, which may lead to the ultimate failure of the liner conduit. Further, monitoring and/or controlling the heat and/or pressure of the material injected into the liner conduit is required in order to appropriately expand the liner conduit within the host conduit. In addition, monitoring and/or controlling various physical parameters in the conduit is important to effectively repair the conduit and engage in the associated process. Accordingly, such prior art systems are deficient in control and are thus subject to failures in installation, maintenance and lining integrity.